Networked control systems are an ubiquitous trend in commercial, industrial and institutional business markets and also in consumer markets. A typical example of a networked control system is a lighting control system with dozens of networked, particularly interconnected light sources. In the future, it is expected that these networked lighting systems will evolve particularly due to new developments on lighting sources such as LED (Light Emitting Diode) luminaries leading to a higher number of light sources. Installation, commissioning, configuration and management of lighting control systems is often complex and also a relevant factor with regard to the total cost of ownership. Particularly the commissioning, which is required for identifying devices and specifying their role in lighting control, is a cumbersome task even in wired lighting control systems with a plurality of switches and luminaries and becomes even more daunting in systems where devices have no wired connections, but only communicate wireless, for example using RF (Radio Frequency) transmissions.
In a lighting control system with wired switches, the assignment of the switches (which luminaire(s) they control) is more or less implicit by the wiring. An installer has connected a switch to a certain port on a controller and thereby the function of the switch is clear. A wireless switch, however, is not physically connected to the system and therefore its assignment is totally undefined immediately after installation. This means an extra burden for a commissioner who has to identify and locate the switches in order to be able to tell the system which switch is which. This is a labour intensive and error prone task.
A straight forward solution to assign wireless switches to luminaires in a lighting control system would be to let the receivers in the luminaires take the switches with the strongest RSSI (received signal strength indication) to be the switches from which they should be controlled: when these switches are pressed, by the installer, all luminaires will receive the signal of each switch, but with different RSSI. In principle, the luminaires in the same room as the switch will measure the highest RSSI from the switch in their room, whereas luminaires in other rooms will see a lower RSSI; the farther they are away, the lower the RSSI in general will be. Due to specific conditions, such as obstructing furniture, doors or even the orientation of the antennas, it can happen that some receivers in the same room as the switch receive the signal with lower strength than some receivers in a neighbouring room. This results in a wrong assignment.
In order to improve commissioning, US2008/0157957A1 discloses a method for commissioning wireless lighting nodes in a building by generating a first map of a network topology of a lighting control system installed in the building using received RSSI values and a second map of the network topology using ToF (Time of Flight) values and comparing the two maps to determine the location of partition walls within the building.